In my high school curriculum, African Americans certainly weren't treated as though they only existed during the Civil Rights movement/slavery....but those subjects are concentrated on for good reason- when teaching "American History", because a class can't cover every single event that ever happened, they must focus on the major events.
To an extent, but there are different ways you can approach those major events. The stories of wars can be taught through accounts of the individual soldiers instead of just names and dates of battles with big coloured arrows labelled with commanders' names on maps. If you've got to show a film about the Civil War, you don't have to show
Gone With the Wind - you could show them
Glory.
Basically, a large part of covering those major historical events is their impact on society, and even if the grand decision-makers involved were white, there isn't an era in the history of the United States when society wasn't made up of a large proportion of African-Americans.
I would also like to add that, early on enough, I don't think there was enough of an African American presence to be recorded...Not that they didn't matter, mind you, but...If nothing noteworthy happened other than their suffering and repression, what else do you expect historians to do? And in US history classes I have taken, they don't usually go into a ton of detail about their history in their native countries because...it's not US history.
Maybe not directly, but those details provide the context for US history, and context is everything. My favourite quote about this was originally made in the context of geology and rock sampling, but I think it's still illuminating:
"If you bring me a dead cat, all I can tell you is that it's a cat and it's dead. But if you tell me that you found it at the side of the highway, I'll reach a completely different set of conclusions than if you tell me you found it in the kitchen of your favourite restaurant."
The American War of 1812 doesn't make any sense historically unless you look at it through the context of the European War of 1812. American slavery doesn't make any sense historically unless you look at it through the context of the empire/colony relationship between Europe and Africa. You don't know the true impact of the American Revolution unless you know about the French Revolution... and on and on.
When it comes to the lack of pre-European American history....Do we have very much historical evidence to teach about? My teachers always enjoyed our sections on Native American peoples, and went into the different groups, their religious rituals, war patterns, allies, enemies, survival methods, etc, etc...
It's not the same as their step-by-step history, but....Perhaps it is the best we can do? Do you know of any surviving historical records of those people? I, personally, don't.... I don't know where they might be found, other than by the word-of-mouth of the people who pass down tales and such....and I know we learned about a few of those.
Pick a Native American group, any group, and there will probably be several books about them and their history listed on Amazon. Your local library may even have some.
In my classes, we went most into depth on the history of the
Six Nations, just because they're the most prominent Native group around here.